This invention relates to a condenser microphone employing an electret as a diaphragm, and relates more particularly to an electret microphone which is reduced in size in a direction perpendicular to the diaphragm.
In condenser microphones an impedance converter is housed in the microphone capsule so as to provide decreased output impedance, and in conventional electret microphones the impedance converter is disposed behind a back electrode plate. This severely limits the ability to reduce the size of the microphone in a direction perpendicular to the diaphragm. Accordingly, in order to effect miniaturization of the microphone, efforts have been made to reduce the radial dimension of the diaphragm; however, reducing the diameter of the diaphragm results in deteriorated tone quality and lowered sensitivity. The prior art microphone is thus comparatively thick and hence is not suitable for use, for example, as an attachment to a tiepin, because it greatly protrudes from a necktie. Further, when a nondirectional microphone of the prior art type is attached to a tiepin, sounds are muffled in the microphone to provide degraded articulation and while this makes the microphone unidirectional, the microphone, due to its thick configuration, nevertheless catches surrounding noises.
An object of this invention is to provide a thin electret microphone.
Another object of this invention is to provide a miniature electret microphone which is excellent in tone quality and high in sensitivity.
Another object of this invention is to provide a thin, unidirectional electret microphone.